1. Field of the Invention
The present invention relates to an information processing apparatus capable of having its main memory expanded while operating.
2. Description of the Related Art
Heretofore, to expand a memory of a system has required three steps: the system is stopped, an additional memory is installed, and the system is restarted. Such techniques are disclosed illustratively in a PC instruction manual, “Hitachi Personal Computer FLORA 1010DI/DM: Your First PC (manual on hardware),” pp. 107–110 (a Japanese publication; Cited Reference 1). This publication describes the need for expanding a memory of a personal computer with its power cable disconnected. Techniques for connecting a device to a system in operation are disclosed in “The Winn L. Rosch Hardware Bible” by Rosch, Winn L, pp. 347–356, published by Samsung America Incorporated (Cited Reference 2). The Cited Reference 2 discusses PCMCIA specifications for allowing memories to be installed or removed while power is being applied. Other techniques for connecting a device to a system in operation are disclosed in the Jun. 2, 1997 issue of Nikkei Electronics (a Japanese publication), pp. 109–112 (Cited Reference 3). Discussed in the Cited Reference 3 are PCI bus specifications for allowing components to be attached or detached during power application.
Because it has been necessary to stop power to the system when a memory is being added thereto, the expansion of memory resources has conventionally required executing two related processes: stopping the system, and initializing the system. In the case of the operating system (OS) generally used in a workstation/server environment, it has typically taken 30 to 60 minutes to stop and initialize the system, including the steps of stopping and initializing application software.
One way of adding a memory during system operation is by having recourse to a cluster system. The cluster system is constituted by a plurality of information processing apparatuses each performing a specific service. In this system, while one apparatus is being stopped, others function to provide their services continuously. One obvious disadvantage of this system is the need for preparing a plurality of information processing apparatuses.